Index: binaries/data/mods/public/gui/gamesetup/gamesetup.js
===================================================================
--- binaries/data/mods/public/gui/gamesetup/gamesetup.js
+++ binaries/data/mods/public/gui/gamesetup/gamesetup.js
@@ -518,6 +518,7 @@
 		"RevealMap": "revealMap",
 		"ExploreMap": "exploreMap",
 		"DisableTreasures": "disableTreasures",
+		"EnableSpies": "enableSpies",
 		"LockTeams": "lockTeams",
 		"LastManStanding" : "lastManStanding",
 		"CheatsEnabled": "enableCheats"
@@ -1421,6 +1422,7 @@
 
 	setGUIBoolean("enableCheats", "enableCheatsText", !!mapSettings.CheatsEnabled);
 	setGUIBoolean("disableTreasures", "disableTreasuresText", !!mapSettings.DisableTreasures);
+	setGUIBoolean("enableSpies", "enableSpiesText", !!mapSettings.EnableSpies);
 	setGUIBoolean("exploreMap", "exploreMapText", !!mapSettings.ExploreMap);
 	setGUIBoolean("revealMap", "revealMapText", !!mapSettings.RevealMap);
 	setGUIBoolean("lockTeams", "lockTeamsText", !!mapSettings.LockTeams);
@@ -1448,7 +1450,7 @@
 
 	for (let ctrl of ["victoryCondition", "wonderDuration", "populationCap",
 	                  "startingResources", "ceasefire", "revealMap",
-	                  "exploreMap", "disableTreasures", "lockTeams", "lastManStanding"])
+	                  "exploreMap", "disableTreasures", "enableSpies", "lockTeams", "lastManStanding"])
 		hideControl(ctrl, ctrl + "Text", notScenario);
 
 	Engine.GetGUIObjectByName("civResetButton").hidden = !notScenario;
Index: binaries/data/mods/public/gui/gamesetup/gamesetup.xml
===================================================================
--- binaries/data/mods/public/gui/gamesetup/gamesetup.xml
+++ binaries/data/mods/public/gui/gamesetup/gamesetup.xml
@@ -407,7 +407,17 @@
 					</object>
 				</object>
 
-				<object name="optionLockTeams" size="14 308 94% 336">
+				<object name="optionEnableSpies" size="14 308 94% 336">
+					<object size="0 0 40% 28" type="text" style="ModernRightLabelText">
+						<translatableAttribute id="caption">Enable Spies:</translatableAttribute>
+					</object>
+					<object name="enableSpiesText" size="40% 0 100% 28" type="text" style="ModernLeftLabelText"/>
+					<object name="enableSpies" size="40%+10 5 40%+30 100%-5" type="checkbox" style="ModernTickBox" hidden="true" tooltip_style="onscreenToolTip">
+						<translatableAttribute id="tooltip">Enable spies on the map.</translatableAttribute>
+					</object>
+				</object>
+
+				<object name="optionLockTeams" size="14 338 94% 366">
 					<object size="0 0 40% 28" type="text" style="ModernRightLabelText">
 						<translatableAttribute id="caption">Teams Locked:</translatableAttribute>
 					</object>
@@ -417,7 +427,7 @@
 					</object>
 				</object>
 
-				<object name="optionLastManStanding" size="14 338 94% 366">
+				<object name="optionLastManStanding" size="14 368 94% 396">
 					<object size="0 0 40% 28" type="text" style="ModernRightLabelText">
 						<translatableAttribute id="caption">Last Man Standing:</translatableAttribute>
 					</object>
@@ -427,7 +437,7 @@
 					</object>
 				</object>
 
-				<object name="optionCheats" size="14 368 94% 396" hidden="true">
+				<object name="optionCheats" size="14 398 94% 426" hidden="true">
 					<object size="0 0 40% 28" type="text" style="ModernRightLabelText">
 						<translatableAttribute id="caption">Cheats:</translatableAttribute>
 					</object>
@@ -437,7 +447,7 @@
 					</object>
 				</object>
 
-				<object name="optionRating" size="14 398 94% 426" hidden="true">
+				<object name="optionRating" size="14 428 94% 456" hidden="true">
 					<object size="0 0 40% 28" hidden="false" type="text" style="ModernRightLabelText">
 						<translatableAttribute id="caption">Rated Game:</translatableAttribute>
 					</object>
@@ -452,7 +462,7 @@
 					name="hideMoreOptions"
 					type="button"
 					style="StoneButton"
-					size="50%-70 428 50%+70 456"
+					size="50%-70 458 50%+70 486"
 					tooltip_style="onscreenToolTip"
 					hotkey="cancel"
 				>
Index: binaries/data/mods/public/gui/session/diplomacy_window.xml
===================================================================
--- binaries/data/mods/public/gui/session/diplomacy_window.xml
+++ binaries/data/mods/public/gui/session/diplomacy_window.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 
 <object name="diplomacyDialogPanel"
-	size="50%-260 50%-200 50%+260 50%+150"
+	size="50%-280 50%-200 50%+280 50%+150"
 	type="image"
 	hidden="true"
 	sprite="ModernDialog"
@@ -35,7 +35,7 @@
 			<translatableAttribute id="caption">E</translatableAttribute>
 			<translatableAttribute id="tooltip">Enemy</translatableAttribute>
 		</object>
-		<object name="diplomacyHeaderTribute" size="430 0 100%-30 100%" type="text" style="DiplomacyText" text_align="center">
+		<object name="diplomacyHeaderTribute" size="430 0 100%-70 100%" type="text" style="DiplomacyText" text_align="center">
 			<translatableAttribute id="caption">Tribute</translatableAttribute>
 		</object>
 	</object>
@@ -55,7 +55,7 @@
 				<object name="diplomacyPlayerEnemy[n]" size="400 0 420 100%" type="button" style="StoneButton" hidden="true"/>
 
 				<!-- Tribute -->
-				<object size="430 0 100%-40 100%">
+				<object size="430 0 100%-80 100%">
 					<repeat count="8" var="r">
 						<object name="diplomacyPlayer[n]_tribute[r]" size="0 0 20 100%" type="button" style="iconButton" tooltip_style="sessionToolTipBold" hidden="true">
 							<object name="diplomacyPlayer[n]_tribute[r]_image" type="image" size="0 0 100% 100%" ghost="true"/>
@@ -63,9 +63,13 @@
 					</repeat>
 				</object>
 
-				<object name="diplomacyAttackRequest[n]" size="100%-20 0 100% 100%" type="button" style="iconButton" tooltip_style="sessionToolTipBold" hidden="true">
+				<object name="diplomacyAttackRequest[n]" size="100%-60 0 100%-40 100%" type="button" style="iconButton" tooltip_style="sessionToolTipBold" hidden="true">
 					<object name="diplomacyAttackRequestImage[n]" type="image" size="0 0 100% 100%" sprite="stretched:session/icons/attack-request.png" ghost="true"/>
 				</object>
+
+				<object name="diplomacySpyRequest[n]" size="100%-20 0 100% 100%" type="button" style="iconButton" tooltip_style="sessionToolTipBold" hidden="true">
+					<object name="diplomacySpyRequestImage[n]" type="image" size="2 2 100%-2 100%-2" ghost="true"/>
+				</object>
 			</object>
 		</repeat>
 	</object>
Index: binaries/data/mods/public/gui/session/menu.js
===================================================================
--- binaries/data/mods/public/gui/session/menu.js
+++ binaries/data/mods/public/gui/session/menu.js
@@ -314,7 +314,16 @@
 
 	g_IsDiplomacyOpen = true;
 
+	updateDiplomacyPanel();
+}
+
+function updateDiplomacyPanel()
+{
+	if (g_ViewedPlayer < 1 || !g_IsDiplomacyOpen)
+		return;
+
 	let isCeasefireActive = GetSimState().ceasefireActive;
+	let hasSharedLos = GetSimState().players[g_ViewedPlayer].hasSharedLos;
 
 	// Get offset for one line
 	let onesize = Engine.GetGUIObjectByName("diplomacyPlayer[0]").size;
@@ -331,6 +340,7 @@
 		diplomacyFormatStanceButtons(i, myself || playerInactive || isCeasefireActive || g_Players[g_ViewedPlayer].teamsLocked);
 		diplomacyFormatTributeButtons(i, myself || playerInactive);
 		diplomacyFormatAttackRequestButton(i, myself || playerInactive || isCeasefireActive || !hasAllies || !g_Players[i].isEnemy[g_ViewedPlayer]);
+		diplomacyFormatSpyRequestButton(i, myself || playerInactive || g_Players[i].isMutualAlly[g_ViewedPlayer] && hasSharedLos);
 	}
 	Engine.GetGUIObjectByName("diplomacyDialogPanel").hidden = false;
 }
@@ -454,6 +464,59 @@
 	}; })(i);
 }
 
+function diplomacyFormatSpyRequestButton(i, hidden)
+{
+	let button = Engine.GetGUIObjectByName("diplomacySpyRequest["+(i-1)+"]");
+	let template = GetTemplateData("special/spy");
+	button.hidden = hidden || !template || GetSimState().players[g_ViewedPlayer].disabledTemplates["special/spy"];
+	if (button.hidden)
+		return;
+
+	button.enabled = controlsPlayer(g_ViewedPlayer);
+	let modifier = "";
+	let tooltips = [translate("Bribe a random unit from this player and share its vision during 10 s.")];
+	if (!button.enabled)
+		modifier = "color:0 0 0 127:grayscale:";
+	else
+	{
+		if (template.requiredTechnology)
+		{
+			let technologyEnabled = Engine.GuiInterfaceCall("IsTechnologyResearched", {
+				"tech": template.requiredTechnology,
+				"player": g_ViewedPlayer
+			});
+			if (!technologyEnabled)
+			{
+				modifier = "color:0 0 0 127:grayscale:"
+				button.enabled = false;
+				tooltips.push(getRequiredTechnologyTooltip(technologyEnabled, template.requiredTechnology, GetSimState().players[g_ViewedPlayer].civ));
+			}
+		}
+
+		if (template.cost)
+		{
+			let neededResources = Engine.GuiInterfaceCall("GetNeededResources", {
+				"cost": template.cost,
+				"player": g_ViewedPlayer
+			});
+			if (neededResources)
+			{
+				if (button.enabled)
+					modifier = resourcesToAlphaMask(neededResources) +":";
+				button.enabled = false;
+				tooltips.push(getNeededResourcesTooltip(neededResources));
+			}
+		}
+	}
+	let icon = Engine.GetGUIObjectByName("diplomacySpyRequestImage["+(i-1)+"]");
+	icon.sprite = modifier + "stretched:session/icons/economics.png";
+	button.tooltip = tooltips.filter(tip => tip).join("\n");
+	button.onpress = (function(i) { return function() {
+		Engine.PostNetworkCommand({ "type": "spy-request", "source": g_ViewedPlayer, "target": i });
+		closeDiplomacy();
+	}; })(i);
+}
+
 function closeDiplomacy()
 {
 	g_IsDiplomacyOpen = false;
Index: binaries/data/mods/public/gui/session/messages.js
===================================================================
--- binaries/data/mods/public/gui/session/messages.js
+++ binaries/data/mods/public/gui/session/messages.js
@@ -517,7 +517,7 @@
 	g_Players = getPlayerData(g_Players);
 
 	if (g_IsDiplomacyOpen)
-		openDiplomacy();
+		updateDiplomacyPanel();
 }
 
 /**
Index: binaries/data/mods/public/gui/session/session.js
===================================================================
--- binaries/data/mods/public/gui/session/session.js
+++ binaries/data/mods/public/gui/session/session.js
@@ -786,6 +786,9 @@
 		if (battleState)
 			global.music.setState(global.music.states[battleState]);
 	}
+
+	if (g_IsDiplomacyOpen)
+		updateDiplomacyPanel();
 }
 
 function onReplayFinished()
Index: binaries/data/mods/public/simulation/components/VisionSharing.js
===================================================================
--- binaries/data/mods/public/simulation/components/VisionSharing.js
+++ binaries/data/mods/public/simulation/components/VisionSharing.js
@@ -1,12 +1,21 @@
 function VisionSharing() {}
 
 VisionSharing.prototype.Schema =
-	"<empty/>";
+	"<element name='Bribable'>" +
+		"<data type='boolean'/>" +
+	"</element>" +
+	"<optional>" +
+		"<element name='Duration' a:help='Duration (in second) of the vision sharing for spies'>" +
+			"<ref name='positiveDecimal'/>" +
+		"</element>" +
+	"</optional>";
 
 VisionSharing.prototype.Init = function()
 {
 	this.activated = false;
-	this.shared = new Set();
+	this.shared = undefined;
+	this.spyId = 0;
+	this.spies = undefined;
 };
 
 /**
@@ -20,7 +29,7 @@
 	let cmpOwnership = Engine.QueryInterface(this.entity, IID_Ownership);
 	if (!cmpOwnership || cmpOwnership.GetOwner() <= 0)
 		return;
-	this.shared.add(cmpOwnership.GetOwner());
+	this.shared = new Set([cmpOwnership.GetOwner()]);
 	Engine.PostMessage(this.entity, MT_VisionSharingChanged,
 		{ "entity": this.entity, "player": cmpOwnership.GetOwner(), "add": true });
 	this.activated = true;
@@ -56,6 +65,12 @@
 				}
 			}
 		}
+
+		// vision sharing due to spies
+		if (this.spies)
+			for (let spy of this.spies.values())
+				if (spy > 0 && spy != owner)
+					shared.add(spy);
 	}
 
 	if (!this.activated)
@@ -73,6 +88,11 @@
 	this.shared = shared;
 };
 
+VisionSharing.prototype.IsBribable = function()
+{
+	return this.template.Bribable == "true";
+};
+
 VisionSharing.prototype.OnDiplomacyChanged = function(msg)
 {
 	this.CheckVisionSharings();
@@ -89,4 +109,57 @@
 		this.CheckVisionSharings();
 };
 
+VisionSharing.prototype.AddSpy = function(player, timeLength)
+{
+	if (!this.IsBribable())
+		return;
+
+	let cmpOwnership = Engine.QueryInterface(this.entity, IID_Ownership);
+	if (!cmpOwnership || cmpOwnership.GetOwner() == player || player <= 0)
+		return;
+
+	let cmpTechnologyManager = QueryPlayerIDInterface(player, IID_TechnologyManager);
+	if (!cmpTechnologyManager || !cmpTechnologyManager.CanProduce("special/spy"))
+		return;
+
+	let template = Engine.QueryInterface(SYSTEM_ENTITY, IID_TemplateManager).GetTemplate("special/spy");
+	let costs = {};
+	for (let res in template.Cost.Resources)
+		costs[res] = Math.floor(ApplyValueModificationsToTemplate("Cost/Resources/"+res, +template.Cost.Resources[res], player, template));
+	let cmpPlayer = QueryPlayerIDInterface(player);
+	if (!cmpPlayer || !cmpPlayer.TrySubtractResources(costs))
+		return;
+
+	// If no duration given, take it from the spy template and scale it with the ent vision
+	// When no duration argument nor in spy template, it is a permanent spy
+	let duration = timeLength;
+	if (!duration && template.VisionSharing && template.VisionSharing.Duration)
+	{
+		duration = ApplyValueModificationsToTemplate("VisionSharing/Duration", +template.VisionSharing.Duration, player, template);
+		let cmpVision = Engine.QueryInterface(this.entity, IID_Vision);
+		if (cmpVision)
+			duration *= 60 / Math.max(30, cmpVision.GetRange());
+	}
+
+	if (!this.spies)
+		this.spies = new Map();
+
+	this.spies.set(++this.spyId, player);
+	if (duration)
+	{
+		let cmpTimer = Engine.QueryInterface(SYSTEM_ENTITY, IID_Timer);
+		cmpTimer.SetTimeout(this.entity, IID_VisionSharing, "RemoveSpy", duration*1000, { "id": this.spyId }); 
+	}
+	this.Activate();
+	this.CheckVisionSharings();
+
+	return this.spyId;
+};
+
+VisionSharing.prototype.RemoveSpy = function(data)
+{
+	this.spies.delete(data.id);
+	this.CheckVisionSharings();
+};
+
 Engine.RegisterComponentType(IID_VisionSharing, "VisionSharing", VisionSharing);
Index: binaries/data/mods/public/simulation/data/technologies/unlock_spies.json
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/data/technologies/unlock_spies.json
@@ -0,0 +1,10 @@
+{
+	"genericName": "Espionage",
+	"description": "Merchants first goal was trading, but they also gathered information on the countries they crossed.",
+	"cost": { "food": 800, "wood": 800, "stone": 500, "metal": 500 },
+	"requirements": { "tech": "phase_city" },
+	"icon": "spy_trader.png",
+	"researchTime": 80,
+	"tooltip": "Allows to bribe other player units and share their vision.",
+	"soundComplete": "interface/alarm/alarm_upgradearmory.xml"
+}
Index: binaries/data/mods/public/simulation/helpers/Commands.js
===================================================================
--- binaries/data/mods/public/simulation/helpers/Commands.js
+++ binaries/data/mods/public/simulation/helpers/Commands.js
@@ -748,6 +748,20 @@
 			cmpAIInterface.PushEvent("AttackRequest", cmd);
 	},
 
+	"spy-request": function(player, cmd, data)
+	{
+		let cmpRangeManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager);
+		let ents = cmpRangeManager.GetEntitiesByPlayer(cmd.target).filter(ent => {
+			let cmpVisionSharing = Engine.QueryInterface(ent, IID_VisionSharing);
+			return cmpVisionSharing && cmpVisionSharing.IsBribable();
+		});
+		let ent = pickRandom(ents);
+		if (ent)
+			Engine.QueryInterface(ent, IID_VisionSharing).AddSpy(cmd.source);
+		else
+			notifySpyFailure(player);
+	},
+
 	"dialog-answer": function(player, cmd, data)
 	{
 		// Currently nothing. Triggers can read it anyway, and send this
@@ -808,6 +822,20 @@
 }
 
 /**
+ * Sends a GUI notification when no units to bribe
+ */
+function notifySpyFailure(player)
+{
+	var cmpGUIInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+	cmpGUIInterface.PushNotification({
+		"type": "text",
+		"players": [player],
+		"message": "There are no bribable units",
+		"translateMessage": true
+	});
+}
+
+/**
  * Get some information about the formations used by entities.
  * The entities must have a UnitAI component.
  */
Index: binaries/data/mods/public/simulation/helpers/Player.js
===================================================================
--- binaries/data/mods/public/simulation/helpers/Player.js
+++ binaries/data/mods/public/simulation/helpers/Player.js
@@ -121,6 +121,12 @@
 		if (disabledTemplates.length)
 			cmpPlayer.SetDisabledTemplates(disabledTemplates);
 
+		if (!settings.EnableSpies)
+		{
+			cmpPlayer.AddDisabledTechnology("unlock_spies");
+			cmpPlayer.AddDisabledTemplate("special/spy");
+		}
+
 		// If diplomacy explicitly defined, use that; otherwise use teams
 		if (getSetting(playerData, playerDefaults, i, "Diplomacy") !== undefined)
 			cmpPlayer.SetDiplomacy(getSetting(playerData, playerDefaults, i, "Diplomacy"));
Index: binaries/data/mods/public/simulation/templates/special/spy.xml
===================================================================
--- /dev/null
+++ binaries/data/mods/public/simulation/templates/special/spy.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Entity>
+  <Cost>
+    <Population>0</Population>
+    <PopulationBonus>0</PopulationBonus>
+    <BuildTime>0</BuildTime>
+    <Resources>
+      <food>0</food>
+      <wood>0</wood>
+      <stone>0</stone>
+      <metal>2000</metal>
+    </Resources>
+  </Cost>
+  <Identity>
+    <Civ>gaia</Civ>
+    <Classes datatype="tokens">Spy</Classes>
+    <GenericName>Spy</GenericName>
+    <RequiredTechnology>unlock_spies</RequiredTechnology>
+  </Identity>
+  <VisionSharing>
+    <Bribable>false</Bribable>
+    <Duration>15</Duration>
+  </VisionSharing>
+</Entity>
Index: binaries/data/mods/public/simulation/templates/template_structure.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_structure.xml
+++ binaries/data/mods/public/simulation/templates/template_structure.xml
@@ -140,7 +140,9 @@
   <Vision>
     <Range>40</Range>
   </Vision>
-  <VisionSharing/>
+  <VisionSharing>
+    <Bribable>false</Bribable>
+  </VisionSharing>
   <VisualActor>
     <ConstructionPreview/>
     <SilhouetteDisplay>false</SilhouetteDisplay>
Index: binaries/data/mods/public/simulation/templates/template_structure_economic_market.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_structure_economic_market.xml
+++ binaries/data/mods/public/simulation/templates/template_structure_economic_market.xml
@@ -48,6 +48,7 @@
       trade_gain_01
       trade_gain_02
       trade_commercial_treaty
+      unlock_spies
     </Technologies>
     <Entities datatype="tokens">
       units/{civ}_support_trader
Index: binaries/data/mods/public/simulation/templates/template_unit.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_unit.xml
+++ binaries/data/mods/public/simulation/templates/template_unit.xml
@@ -124,6 +124,9 @@
   <Vision>
     <Range>12</Range>
   </Vision>
+  <VisionSharing>
+    <Bribable>false</Bribable>
+  </VisionSharing>
   <VisualActor>
     <SilhouetteDisplay>true</SilhouetteDisplay>
     <SilhouetteOccluder>false</SilhouetteOccluder>
Index: binaries/data/mods/public/simulation/templates/template_unit_mechanical_ship_merchant.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_unit_mechanical_ship_merchant.xml
+++ binaries/data/mods/public/simulation/templates/template_unit_mechanical_ship_merchant.xml
@@ -63,4 +63,7 @@
   <Vision>
     <Range>50</Range>
   </Vision>
+  <VisionSharing>
+    <Bribable>true</Bribable>
+  </VisionSharing>
 </Entity>
Index: binaries/data/mods/public/simulation/templates/template_unit_support_trader.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_unit_support_trader.xml
+++ binaries/data/mods/public/simulation/templates/template_unit_support_trader.xml
@@ -50,4 +50,7 @@
   <Vision>
     <Range>60</Range>
   </Vision>
+  <VisionSharing>
+    <Bribable>true</Bribable>
+  </VisionSharing>
 </Entity>